docs: def install_salt_support(from_ppa=True):
      """Installs the salt-minion helper for machine state.
  
      By default the salt-minion package is installed from
      the saltstack PPA. If from_ppa is False you must ensure
      that the salt-minion package is available in the apt cache.
      """
      if from_ppa:
          subprocess.check_call([
              '/usr/bin/add-apt-repository',
              '--yes',
              'ppa:saltstack/salt',
          ])
          subprocess.check_call(['/usr/bin/apt-get', 'update'])
      # We install salt-common as salt-minion would run the salt-minion
      # daemon.
      charmhelpers.fetch.apt_install('salt-common')